Multiple stage vacuum tube



Feb. 17, 1942. g 5. AMBER-SEN 2,273,003

MULTIPLE STAGE VACUUM TUBE Filed Jan. 28, 1941 2 Sheets-Sheet lINVENTORT CHRIS s. ANDERSEN,

ATTORMS'YS.

Feb. 17, 1942. c. s. ANDERSEN 2,273,003

MULTIPLE STAGE VACUUM TUBE Filed Jan. 28, 1941 '2 Sheets-Sheet2 IN V ENTOR,

cHk/s s. ANDERSN, BY

,arromvsrs.

Patented Feb. 17, 1942 "i" QFFICE 7 Claims.

My invention relates to grid controlled vacuum tubes and moreparticularly to a means of supporting the elements of an electronic tubein such a manner that a plurality of stages or individual electrodeassemblies may be mounted within the same envelope.

Among the objects of my invention are:

To provide means for rigidly supporting electrodes in such a manner thata plurality of individual units may be enclosed in a single envelope; toprovide a means and method of energizing a plurality of symmetricallydisposed electrode assemblies from a single cathode; to provide aplurality of electrodes for a multistage electron discharge tube whichcan be assembled at minimum cost; to provide a means and method ofsupporting, and electrically operating a plurality of electrodeassemblies in a single envelope; to provide a small, compact multistagetube ideally adapted for use in hearing aids and similar low weightdevices; and to provide a simple and efiicient multistage vacuum tube.

Other objects of my invention will be apparent or will be specificallypointed out in the description forming a part of this specification, butI do not limit myself to the embodiment of the invention hereindescribed, as various forms may be adopted within the scope of theclaims.

In the drawings Fig. 1 is a view partly in section, and partly inelevation of one form of my invention, having three stages therein.Figs. 2, 3, 4, and 5 are views partly in section and partly in elevationtaken as indicated by the lines 2-2, 33, 44, and 5-5, respectively, inFig 1. Fig. 6 is a wiring diagram showing how a six-stage tube made inaccordance with my invention may be energized as an efiicient multistageamplifier.

Referring to the drawings for a more detailed description of myinvention, an envelope l is provided at one end thereof with a stem 2closed at the top by the customary press 3 through which lead-in wiresare passed and the supporting elements are embedded. The main support ofelectrodes comprises a pair of relatively heavy support rods 5 extendingupwardly from the press, these support rods being provided with lead-inwires 6. Individual electrode assemblies are mounted on support rods 5and may be assembled from the top.

First to pass over the rods is a lower mica washer I having a centralaperture 9 therein,

the rods passing through peripheral apertures in the washer, andsupported on beads [0. Immediately over the mica washer l is positioneda ceramic disc II, this disc having a central aperture l2 and acounterbore 53. The aperture 9 in mica disc I is smaller than theaperture l2 in the ceramic disc II, and a grid I4 in the form of aspiral having the end turns thereof closer together than theintermediate turns, is dropped into central aperture l2 in ceramic discll with the end turns filling the aperture. A cylindrical anode I 5,either solid as shown, or mesh screen, has one end thereof inserted intocounterbore l3, this anode being shorter than the length of grid l4. Asecond ceramic disc l6, similarly bored and counterbored to disc H isthen inverted over the grid-anode assembly, being held against gravityby resting on the upper edges of both anode and grid. A mica washer 'l'is then dropped over the rods 5, this washer having an aperture 9'similar to washer 1-. The assembly may then be continued upwardly withrid M and anode 15' held by the discs II and IS. A third washer 1" maythen be added and a third stage comprising grid l4" and anode I5" heldby the discs H" and It". A top wash-' er 7" is then used to cap theelectrode assembly. The assembly may be held in place by top beads 200mtop of washer 1" and if desired, additional rods 2| may be added,passing through all washers at the periphery thereof from rods 5. Theserods may be used as connections from various electrodes.

It will be seen that in the serial assembly of washers, discs, andelectrodes, as described, an axially clear space is left through which afilament 22 may be passed, without touching any of the tube structures.At the lower end the filament 22 is welded to bar 24 attached to one rod5, and at the upper end filament 22 is attached to filament spring 25which is formed with a recurved portion 26 to which the upper end of thefilament is attached. Filament tension can be easily adjusted and thefilament may be accurately centered with such a recurved spring.

All connections to grids and anodes are brought out separately throughthe press, and I prefer to attach connections 21, 21' and 21" to theanodes on the exterior thereof, between the ceramic discs, and bringthem downwardly to meet the lead wires. For example, the upper anode l5"may be connected by wire 21" to one of rods2l. The upper grid It may beconnected by wire 28" passing between disc II" and washer l" to oppositerod 21!. Anode wire 21 may be brought out laterally and then downwardlythrough apertures 30 in washers I and 1. The wire 29' to grid M isconnected to the lower end of the grid and is brought out between theadjacent ceramic disc and mica washer to the edge of the mica. washerand is then passed downwardly through grid wire apertures 32 in thevarious mica washers. Grid l4 may be connected through wire 28 passingbetween washer and. disc I|, thence to a lead-in wire through anaperture 3| in disc 7. Thus the anode and grid wires are well separatedand preferably run to opposite sides of the various mica washers toreduce capacity effects.

After the assembly of as many stages as desired is accomplished, thetube may be pumped and sealed in the customary manner, through theexhaust tip 35 at the top of the tube. Obviously, however, otherpositions of the exhaust tip may be provided, as is well known in theart.

I have found that tubes made in the manner just above described may bequickly and easily assembled to provide substantially as many stages asmay be desired and in an extremely small space. For example, I have madea fourstagetube in this manner, which is only half an inch in diameterand an inch and a half long, and a six-stage tube is very little longer.Such a tube is ideally adapted for use in hearing aids where weight andspace are at a premium.

I should like to point out, however, that it is not necessary that allstages of the tube of my invention have the same characteristics. WhileI have shown all grids and anodes in Fig. 1 as being identical, it willbe obvious that each individual stage may be designed t have differentand desirable characteristics, as is well known in the art.

In Fig. 6 I have shown one circuit which is ideally adapted for use witha six-stage amplifier tube built according to the design of Fig. 1 with,however, the different stages slightly changed to provide the desiredresults. In this case an input device 40, such as a crystal microphone,is coupled to first stage 4| through a capacity 42. In Fig. 6 I haveshown each stage as a conventional trlode but it should be fullyunderstood that all of these stages are contained within the sameenvelope. Grid 44 of stage 4| is maintained positive with respect to itscathode portion 45 through resistor 46 energized by battery 41 throughgrid supply line 49. Th anode of stage 4| is also positively energizedthrough resistor 5|. The plate impedance of this stage is very high andthe anode 50 thereof is coupled to grid 52 of the second stage 54through capacity 55. Inasmuch as the impedance of stage 54 must also behigh, grid 52 thereof is biased through variable resistor 56 to biasline 5'! which connects through resistor 59 to one side of input device40, thus making the grid having a bias common to the cathode orfilament. The amplification of stage 54 is low, allowing high gridimpedance. Stage 6!] is a duplicate of stage 4| and preferably has ahigh amplification factor. Stage 6| is a low amplification stage andtherefore it is biased similarly to stage 54. Its purpose is to invertthe signal Without any amplification, which may be accomplished bymaking resistor 64 of low resistance. The signal, is then delivered tostage 65 which has a medium amplification factor and acts as one-half ofthe output stage. Stage 56 is the other half of the output stage and isenergized through line 57 from stage 60. Thus the output stage can beclass B, stage Gil, or stage 6|, acting through 180 cf the signal. Theoutput voltage will be greater than with a single stage output, andpotentials can be provided through resistors 69 to the output stage sothat a crystal output device 10 for example, can be connected directlyto the anodes of stages 65 and 66 without constant potential appearingon the output device. The advantage of such an output arrangement is togenerate a large signal with a small anode voltage, thus making thecircuit ideally adapted for use in hearing aids, for example. Thecathode 45 is energized through a cathode battery under control of acathode switch 12.

Thus I have described a multiple stage vacuum tube that can be easilyassembled in a very small envelope and which can be used in multistageform with relatively low potentials, to provide a compact, eflicienttube and circuit for use where weight and space are at a premium, such ain hearing aids.

I claim:

1. In a multi-stage vacuum tube having an envelope and a presssupporting upright parallel main support rods, an electrode assemblycomprising a thin refractory washer mounted on said rod, a ceramic discon said washer inside of said rods, said washer and said disc havingcoaxial bores therein, and said disc having an additional counter-bore,a grid having end turns spaced closer than intermediate turns thereofmounted with said end turns fitting the bore of said disc with the endof said grid resting on said washer, an anode mounted to fit in saiddisc counter-bore, a second disc positioned inside of said rod andinverted over said grid and anode, said second disc having a centralbore coaxial with the bore of said first disc, said sec ond disc havingfirst and second counter-bores, said first counter-bore fitting theopposite closer end turns of said grid, and said second counterborefitting the opposite end of said anode, said opposed discs forming thesole positioning and supporting means for said grid and anode, a secondcentrally bored washer positioned over said second disc and mounted onsaid rod, and means for preventing said second washer from moving alongsaid rod, said second washer thereby holding said assembly in place, anda filament passing through said discs, washers and grid.

,2. In a multistage vacuum tube having an envelope and a presssupporting upright parallel main support rods, an electrode assemblycomprising a thin refractory washer mounted on said rods, a ceramic discon said washer, said washer and said disc having coaxial bores thereinand said disc having in addition a counterbore, a grid having end turnsspaced closer than intermediate turns thereof, mounted in the bore ofsaid disc and resting on said washer, an anode mounted in said disccounterbore, a similar disc and washer inverted over said grid andanode, means on said rod to position said washers, and a filamentpassing through said discs, washers and grid.

3. A tube in accordance with claim 1 wherein a lead to said anode isbrought out between said discs and a lead to said grid is brought outbetween a disc and a washer.

4. A tube in accordance with claim 1 wherein a lead to said anode isbrought out between said discs and a lead to said grid is brought outbetween a disc and a washer, said leads being brought out in oppositedirections.

5. A tube in accordance with claim 1 wherein a lead to said anode isbrought out between said discs and a lead to said grid is brought outbetween a disc and a washer, said leads being brought Out in Opposite ren d Short a plurality of superimposed units are assembled ppo ods spaced90 from said main support on said main rods, with the top washer of onerods and passing through both of said washers. unit acting as the lowerwasher of the unit 6. A tube in accordance with claim 1 wherein above,with said filament passing axially through said filament is connected ateach end to a. main 5 all of aid units,

support rod. CHRIS S. ANDERSEN.

7. A tube in accordance with claim 1 wherein

